diff --git a/core/lib/Drupal/Core/Entity/Field/PrepareCacheInterface.php b/core/lib/Drupal/Core/Entity/Field/PrepareCacheInterface.php
index 6cdf575..7f57c53 100644
--- a/core/lib/Drupal/Core/Entity/Field/PrepareCacheInterface.php
+++ b/core/lib/Drupal/Core/Entity/Field/PrepareCacheInterface.php
@@ -10,26 +10,25 @@
 /**
  * Interface for preparing field values before they enter cache.
  *
- * If a field type implements this interface, the getCacheValue() method will be
- * invoked instead of getValue().
- *
+ * If a field type implements this interface, this method will be used instead
+ * of the regular getValue() to collect the data to include in the cache of
+ * field values.
  */
 interface PrepareCacheInterface {
 
   /**
-   * Massages loaded field values before they enter the field cache.
+   * Returns the data to store in the field cache.
    *
-   * You should never load fieldable entities within this method, since this is
-   * likely to cause infinite recursions. Use the prepareView() method instead.
+   * This method is called if the entity type has field caching enabled, when an
+   * entity is loaded and no existing cache entry was found in the field cache.
    *
-   * Also note that the method is not called on field values displayed during
-   * entity preview. If the method adds elements that might be needed during
-   * display, you might want to also use prepareView() to add those elements in
-   * case they are not present.
+   * This method should never trigger the loading of fieldable entities, since
+   * this is likely to cause infinite recursions. A common workaround is to
+   * provide a base formatter class implementing the prepareView() method
+   * instead.
    *
-   * The method is also only called if the entity has field caching enabled. The
-   * recommended way to implement it is by providing a computed field item
-   * property that an also hold a value set with setValue(). See
+   * The recommended way to implement it is to provide a computed field item
+   * property that can accepts setting a value through setValue(). See
    * \Drupal\text\Plugin\field\field_type\TextItemBase and the corresponding
    * computed property Drupal\text\TextProcessed for an example.
    */
diff --git a/core/modules/datetime/lib/Drupal/datetime/Plugin/field/field_type/DateTimeItem.php b/core/modules/datetime/lib/Drupal/datetime/Plugin/field/field_type/DateTimeItem.php
index d7e6272..c5df7ea 100644
--- a/core/modules/datetime/lib/Drupal/datetime/Plugin/field/field_type/DateTimeItem.php
+++ b/core/modules/datetime/lib/Drupal/datetime/Plugin/field/field_type/DateTimeItem.php
@@ -148,10 +148,7 @@ public function isEmpty() {
    * {@inheritdoc}
    */
   public function onChange($property_name) {
-    // Notify the parent of changes.
-    if (isset($this->parent)) {
-      $this->parent->onChange($this->name);
-    }
+    parent::onChange($property_name);
 
     // Enforce that the computed date is recalculated.
     if ($property_name == 'value') {
diff --git a/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php b/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php
index 9ac29f3..fc6be34 100644
--- a/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php
+++ b/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php
@@ -344,11 +344,4 @@ public function getUploadValidators() {
     return $validators;
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  public function prepareCache() {
-    return $this->getValue();
-  }
-
 }